Search Publications
A Helium Spread among the Main-Sequence Stars in NGC 2808
D'Antona, F.; Bellazzini, M.; Galleti, S. +3 more
We have made a detailed study of the color distribution of the main sequence of the globular cluster (GC) NGC 2808, based on new deep HST WFPC2 photometry of a field in the uncrowded outskirts of the cluster. The observed color distribution of main-sequence stars is not Gaussian and is wider than expected for a single stellar population, given our…
The Mass Assembly Histories of Galaxies of Various Morphologies in the GOODS Fields
Conselice, Christopher J.; Ellis, Richard S.; Bundy, Kevin
We present an analysis of the growth of stellar mass with cosmic time partitioned according to galaxy morphology. Using a well-defined catalog of 2150 galaxies based, in part, on archival data in the Great Observatories Origins Deep Survey (GOODS) fields, we assign morphological types in three broad classes (ellipticals, spirals, peculiar/irregula…
Decay of Planetary Debris Disks
Bryden, G.; Stapelfeldt, K. R.; Rieke, G. H. +9 more
We report new Spitzer 24 µm photometry of 76 main-sequence A-type stars. We combine these results with previously reported Spitzer 24 µm data and 24 and 25 µm photometry from the Infrared Space Observatory and the Infrared Astronomy Satellite. The result is a sample of 266 stars with mass close to 2.5 Msolar, all detec…
Strong-Lensing Analysis of A1689 from Deep Advanced Camera Images
Herranz, D.; Zheng, W.; Broadhurst, Tom +39 more
We analyze deep multicolor Advanced Camera images of the largest known gravitational lens, A1689. Radial and tangential arcs delineate the critical curves in unprecedented detail, and many small counterimages are found near the center of mass. We construct a flexible light deflection field to predict the appearance and positions of counterimages. …
Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-based Measurement of the Black Hole Mass
Kaspi, Shai; Laor, Ari; Moran, Edward C. +8 more
A reverberation-mapping program on NGC 4395, the least luminous known Seyfert 1 galaxy, undertaken with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope yields a measurement of the mass of the central black hole MBH=(3.6+/-1.1)×105 Msolar. The observations consist of two visits of five orbits …
Direct Observations of the Magnetic Reconnection Site of an Eruption on 2003 November 18
Raymond, J. C.; Ko, Y. -K.; Lin, J. +5 more
We report direct observations of the magnetic reconnection site during an eruptive process that occurred on 2003 November 18. The event started with a rapid expansion of a few magnetic arcades located over the east limb of the Sun and developed an energetic partial-halo coronal mass ejection (CME), a long current sheet, and a group of bright flare…
An X-Ray Study of Magnetic Field Strengths and Particle Content in the Lobes of FR II Radio Sources
Hardcastle, M. J.; Croston, J. H.; Birkinshaw, M. +3 more
We present a Chandra and XMM-Newton study of X-ray emission from the lobes of 33 classical double radio galaxies and quasars. We report new detections of lobe-related X-ray emission in 11 sources. Together with previous detections, we find that X-ray emission is detected from at least one radio lobe in ~75% of the sample. For all of the lobe detec…
Measurement of Spin-Orbit Alignment in an Extrasolar Planetary System
Butler, R. Paul; Vogt, Steven S.; Marcy, Geoffrey W. +10 more
We determine the stellar, planetary, and orbital properties of the transiting planetary system HD 209458 through a joint analysis of high-precision radial velocities, photometry, and timing of the secondary eclipse. Of primary interest is the strong detection of the Rossiter-McLaughlin effect, the alteration of photospheric line profiles that occu…
Reflections of Active Galactic Nucleus Outbursts in the Gaseous Atmosphere of M87
Churazov, E.; Vikhlinin, A.; Forman, W. +7 more
We combined deep Chandra, ROSAT HRI, and XMM-Newton observations of M87 to study the impact of active galactic nucleus (AGN) outbursts on its gaseous atmosphere. Many X-ray features appear to be a direct result of repetitive AGN outbursts. In particular, the X-ray cavities around the jet and counterjet are likely due to the expansion of radio plas…
Helioseismological Implications of Recent Solar Abundance Determinations
Pinsonneault, Marc; Basu, Sarbani; Bahcall, John N. +1 more
We show that standard solar models are in good agreement with the helioseismologically determined sound speed and density as a function of solar radius, the depth of the convective zone, and the surface helium abundance, as long as those models do not incorporate the most recent heavy-element abundance determinations. However, sophisticated new an…